1. Field of the Invention Deferent
The present invention relates to seat reclining mechanisms for adjusting a tilt angle of a seat back of a seat (e.g., a vehicle seat).
2. Description of the Related Art
Typically, a vehicle seat comprises a seat back and a seat cushion. The seat back and the seat cushion are rotatably interconnected via a seat reclining mechanism for adjusting a tilt angle of the seat back. Such a seat reclining mechanism is taught, for example, by Japanese Laid-Open Patent Publication Number 2002-10851. Such a seat reclining mechanism is known as a “round type” seat reclining mechanism.
As shown in FIG. 11, the known seat reclining mechanism includes a pair of opposing disk-like housings, i.e., a first or stationary housing 11 and a second or rotational housing 12. The first housing 11 is affixed to the vehicle seat cushion (not shown). The second housing 12 is affixed to the vehicle seat back (not shown). The first and second housings 11 and 12 are circumferentially connected by an annular fastener or clip ring 2 along peripheral edges 11a and 12a thereof, so that the second housing 12 can move or rotate relative to the first housing 11 around a rotational shaft (not shown).
The clip ring 2 comprises an annular guide portion 2a that slidably support the peripheral edge 12a of the second housing 12 and an annular fixture portion 2b that is fixed to the peripheral edge 11a of the first housing 11. The guide portion 2a is circumferentially formed with a plurality of projections or slide portions 2a-1, so that a sliding clearance between the second housing peripheral edge 12a and the clip ring guide portion 2a can be easily controlled. As shown in FIG. 10, the slide portions 2a-1 are spaced at equal intervals. The first and second housing 11 and 12 thus assembled are respectively fixed to the seat cushion and the seat back.
The seat reclining mechanism further includes a locking means (not shown) that can prevent the second housing 12 from rotating relative to the first housing 11, so as to lock the seat reclining mechanism. The locking means essentially consists of a cam member and a pair of pawls (not shown) that are received within the housings 11 and 12. The cam member is secured to or integrally formed with the rotational shaft, so as to rotate with the rotational shaft. Each of the pawls is provided with a convex toothed portion and is radially movably positioned on the first housing 11.
When the rotational shaft is rotated to a locking position, the pawls are radially moved outward by the cam member, so that the respective convex toothed portions of the pawls engage a concave toothed portion (not shown) that is circumferentially formed over an inner circular surface of the second housing peripheral edge 12a. In this state, the second housing 12 is prevented from rotating relative to the first housing 11, so that the seat reclining mechanism is locked. As a result, the seat back is locked in position relative to the seat cushion.
Often times, a large force can be unexpectedly applied to the seat reclining mechanism in a direction to separate the housings 11 and 12 from each other. Such a large force may concentrate to the slide portions 2a-1 of the clip ring guide portion 2a. As a result, the guide portion 2a may be deformed outwardly or spread out, as shown by a broken line in FIG. 11. Such a deformation of the guide portion 2a may reduce a locking performance of the seat reclining mechanism.